Cost of second M1 'must be determined'

Money for a study determining the cost of a second M1 highway should be included in the Queensland budget, according to the state's peak infrastructure group.

The Palaszczuk government won't prioritise the project despite increasing its infrastructure spend in next month's budget to $45 billion over four years, the highest level since the 2011 flood recovery.

It has instead put its focus on the Cross River Rail project and a long-awaited upgrade to the Pacific Motorway. The state opposition has promised to forge ahead with the second M1 if elected.

Both major parties have contrasting views about its cost, with Labor valuing it at more than $2 billion but the Liberal National Party opposition is confident it can be delivered for around $1 billion.

Steve Abson, of the Infrastructure Association of Queensland, says an accurate figure for the road between Stapylton and Nerang must be established via a study funded in the budget.

"That would be a really prudent step," he told AAP.

"Rather than guess whether it's anywhere between a billion and $2.4 billion, which is obviously a wide range, we need to invest in a business case to properly assess what the cost-benefit really is.